Real Madrid's Marcelo, centre, was on the receiving end of alleged racist remarks made by the Barcelona midfielder Sergio Busquets during the Champions League semi-final first leg. Photograph: Lluis Gene/AFP/Getty Images

Real Madrid opened a new front in the propaganda war with Barcelona by releasing footage of Barcelona's Sergio Busquets allegedly mouthing "mono, mono [monkey, monkey]" at their black Brazilian full-back, Marcelo. Both protagonists in the most unseemly Champions League tie in memory are in a state of full mobilisation.

The alleged Busquets insult is delivered slyly, from behind a hand raised to his mouth to reduce the risk of detection: more bad acting by the most inept thespian in the competition. Of all the accusations flying around, this is the most serious, and shows both the depths to which this semi-final has descended and the extent to which YouTube, websites, video compilations and complaints to Uefa are now being used as political tools by Spain's most powerful clubs.

With Barça leading 2-0, thanks to the redemptive brilliance of Lionel Messi, this is a truly dirty fight that will shape future relations between the two empires. Overwhelmed by the tide of objections from either side, Uefa rejected both sets of grievances. Lawyers at the Bernabéu and Camp Nou may regard that outcome as a victory: mutually assured inaction.

Real had asked Uefa to act against six Barcelona players for "premeditated anti-sporting behaviour", a charge they extended to José Mourinho's nemesis, Pep Guardiola, who was accused of orchestrating the theatrics. Mourinho's club were amusingly precise in their demands. They wanted two-game bans for Busquets, Dani Alves and Pedro and one-game suspensions for Seydou Keita, Víctor Valdés and Javier Mascherano. Barcelona had already complained to Uefa about Mourinho's post-match rant about supposed Catalonian influence over referees, in which he claimed Guardiola had never won a "clean" European Cup.

Europe's governing body, meanwhile, had filed five charges against Madrid relating to the throwing of missiles, a pitch invasion, Pepe's red card, Mourinho's sending-off and the "inappropriate statement" served up by the Real coach at the post-match press conference.

Somewhere in all this a second football match waits to be played – and refereed by the Belgian Frank De Bleeckere, who was one of five match officials named by Mourinho on Wednesday night as part of his J'Accuse. De Bleeckere sent off Thiago Motta for pushing Busquets in the face after 27 minutes when Mourinho's Inter team met Barcelona at Camp Nou in last year's semi-finals. Busquets distinguished himself with a peek-a-boo gesture to check the referee's reaction as he lay on the ground with an apparently life-threatening facial injury.

The appointment of De Bleeckere is bound to be seen by Real and Mourinho as another provocation by Uefa, which they suspect of favouring Barcelona. When the name of the referee was announced yet another contentious issue was added to the toxic brew of Catalan-Castillian hatred. "I've known for about a week that I'd got a semi-final and I've been focused on that. I've sort of put myself in exile," said De Bleeckere, who is close to retirement (not close enough, he may feel by the end of the 90 minutes).

In this marathon of review and counter-accusation the clubs appear to hope their own misdemeanours will be drowned out by moral and legal noise. The ferocity of the attacks is unprecedented. But they look orchestrated, too, by lawyers and communications directors, to lift each team off their hook. Digital age outlets (Twitter, in-house TV stations) have served the purposes of dissemination. This precedent will be studied and copied for future footballing disputes.

Real were especially meticulous in calling Barcelona's play-actors to account. A video on their website is headed. "Television images show that Pepe did not touch Alves's leg [for the sending off]," and proceeds to depict Barcelona players rolling around and clutching faces to deceive Wolfgang Stark, the German referee. Pedro is another of Guardiola's players who Real evidently think should be at Rada. In response, some Barça supporters have claimed the Alves clip was doctored, with the frames showing contact removed.

"The sports world cries out" was the emotive headline on a piece of Real prose that claimed stars across the firmament were denouncing Barcelona's dishonesty. No mention was made of the comparable disgust expressed in reaction to Mourinho's insinuations about Uefa and referees. Naturally Real were loading pressure on De Bleeckere not to "fall for Barcelona's theatre" (their words); and the allegations of racism against Busquets could be seen as the final, pre-match nuclear option to swing public opinion Madrid's way.

Both teams lost at the weekend, which may reflect the emotional toll last week's events had on the players. As each club sought the highest moral ground, Barcelona received a boost from Ottmar Hitzfeld, one of only three coaches to win the European Cup with two clubs (Mourinho and Ernst Happel are the others.) In Kicker, Hitzfeld wrote: "Luckily, Mourinho's destructive tactics, aimed solely at provoking and destroying the opposition's gameplan, did not work.

"Such a way of playing does not relate to the demands of Real, it's really shameful for Real Madrid. It harms the good name and image of this legendary club. I've met him [Mourinho] at Uefa meetings and his behaviour is faithful to his image: arrogant, haughty, chewing gum and somewhat of a boor. Barça should make him pay on the pitch."